1. Field of the Invention
The present invention relates to a vaporizer, and more particularly, to a vaporizer delivery system comprising a sublimatable solid precursor material applied to a wire substrate for vaporizing and achieving a continuous uninterrupted delivery of a vaporized precursor to a downstream semiconductor process chamber.
2. Description of the Related Art
Chemical vapor deposition (CVD) has been extensively used for preparation of films and coatings in semiconductor wafer processing. CVD is a favored deposition process in many respects, for example, because of its ability to provide highly conformable and high quality films, at relatively fast processing times. Further, CVD is beneficial in coating substrates of irregular shapes including the provision of highly conformable films even with respect to deep contacts and other openings.
In general, CVD techniques involve the delivery of gaseous reactants to the surface of a substrate where chemical reactions takes place under temperature and pressure conditions that are favorable to the thermodynamics of the desired reaction. The type and composition of the layers that can be formed using CVD is limited by the ability to deliver the reactants or reactant precursors to the surface of the substrate. Various liquid reactants and precursors are successfully used in CVD applications by delivering the liquid reactants in a carrier gas. In liquid reactant CVD systems, the carrier gas is typically bubbled at a controlled rate through a container of the liquid reactant so as to saturate the carrier gas with liquid reactant, and the saturated carrier then is transported to the reaction chamber.
Analogous attempts have been made to deliver solid reactants to a CVD deposition chamber, but with much less success. The delivery of solid precursors in CVD processing is carried out using the sublimator/bubbler method in which the precursor typically is placed in a sublimator/bubbler reservoir, which then is heated to the sublimation temperature of the precursor to transform it into a vapor for transport into the CVD reactor with a carrier gas such as argon, or nitrogen. The carrier gas mixes with the vapor, and is then transported to the deposition chamber.
However, this procedure has been unsuccessful in reliably and reproducibly delivering a solid precursor to the reaction chamber for a number of reasons. Initially, it is difficult to ensure complete saturation of the fast flowing carrier gas stream because of the limited amount of exposed surface area of the solid precursor in the vaporizer system and need for uniform temperature to provide maximum sublimation. This problem may be alleviated by using large excesses of precursor material beyond the amount needed for film growth. However, using an excess of material can result in a substantial waste of precursor materials.
Further, it is difficult to vaporize a solid at a controlled rate such that a reproducible flow of vaporized solid precursor can be delivered to the process chamber. Lack of control of solid precursor sublimation is, at least in part, due to the changing surface area of the bulk solid precursor as it is vaporized. Such a changing surface area when the bulk solid precursor is exposed to sublimation temperatures produces a continuously changing rate of vaporization, particularly for thermally sensitive compounds. This ever-changing rate of vaporization results in a continuously changing and non-reproducible flow of vaporized solid precursor for deposition in the process chamber. As a result, processes using such vaporized solid precursors cannot be controlled adequately and effectively.
Accordingly, there is a need in the art for a vapor delivery system for delivering solid precursors, particularly thermally sensitive precursors, which efficiently vaporizes solid precursor materials at a highly controllable and reproducible flow rate.
The present invention relates to a vaporizer system and method for vaporizing solid precursor source materials having particular utility for semiconductor manufacturing applications.
In one aspect, the present invention relates to a vapor delivery system for vaporization and delivery of a solid source material that provides sufficient surface area of the solid source material to meet the flow rates required for typical deposition applications.
Accordingly, the present invention provides for a system for delivering a precursor vapor, said system comprising:
a. a solid precursor vaporization chamber;
b. an elongate support having a vaporizable solid precursor coated thereon:
c. means for
i) translating the elongate support having the vaporizable solid precursor coated thereon through the chamber so that a length of the elongate support having the vaporizable solid precursor coated thereon is exposed for vaporization of said vaporizable solid precursor in said chamber, and
ii) translating out of the chamber the elongate support from which the solid precursor has been vaporized;
d. means for heating the exposed length of the elongate support having the vaporizable solid precursor coated thereon in said chamber; and
e. means for discharging precursor vapor from said chamber.
In the present invention the elongated support may include, but is not limited to, screens, meshes, webs, wires, fibers, multifilament ropes, chain structures, and ribbons. The support may further comprises an electrically resistively heatable element that can be electrically heated to a temperature for vaporizing said solid precursor coated on the elongate support. Preferably, the elongated support is a wire element connected to a dispensing spool arranged for continuous feed of the wire element through the internal chamber. Further, the solid precursor depleted wire element can be rewound on an uptake spool positioned adjacent to the chamber.
In another aspect, the present invention relates to a vapor delivery system for vaporization and delivery of a precursor, comprising:
a. a sealable housing comprising an internal chamber;
b. a gas inlet port in fluid communication with the internal chamber for introducing a carrier gas;
c. a first rotatable spool positioned adjacent to the housing;
d. a wire coated with a sublimatable solid precursor material having one end connected to first rotatable spool and spooled thereon;
e. a heating means communicatively connected to the internal chamber to heat at least a portion of the internal chamber thereby providing a heated area at the sublimation temperature of the sublimatable solid precursor material;
f. at least one drive mechanism for unspooling and moving the coated wire through the heated area wherein the sublimatable solid precursor material is vaporized forming a precursor gas and a substantially uncoated wire; and
g. a gas outlet port for passage of the precursor gas from the internal chamber to a downstream processing unit.
The delivery system may further comprise a second rotatable spool for spooling of the uncoated wire, wherein the second rotatable spool can be connected to the drive mechanism and positioned a distance from the first rotatable spool and adjacent to the housing.
Solid precursors useful in the present invention include but are not limited to, elemental boron, copper and phosphorus; decaborane; metal halides such as gallium halides, indium halides, antimony halides, arsenic halides, gallium halides, aluminum iodide, titanium iodide; metalorganic complexes, such as, cyclopentadienylcycloheptatrienyltitanium (CpTiCht), cyclooctatetraenecyclopentadienyltitanium, biscyclopentadienyltitanium-diazide, In(CH3)2(hfac), dibromomethyl stibine and tungsten carbonyl, as well as metalorganic xcex2-diketonate complexes, metalorganic alkoxide complexes, metalorganic carboxylate complexes, metalorganic aryl complexes and metalorganic amido complexes.
Other solid precursor compositions useful in specific applications of the instant invention are disclosed in the following United States Patents, which are commonly owned by the assignee of the present application and hereby incorporated herein by reference in their entireties:
U.S. patent application Ser. No. 09/414,133 in the names of, Thomas H. Baum and Witold Paw, which was issued as U.S. Pat. No. 6,399,208 on Jun. 4, 2002;
U.S. patent application Ser. No. 09/218,992 filed 22 Dec. 1998, in the names of, Chongying Xu and Thomas H. Baum, which was issued as U.S. Pat. No. 6,204,402 on Mar. 20, 2001;
U.S. patent application Ser. No. 08/960,915 filed 30 Oct. 1997, in the names of, Thomas H. Baum, et al., which was issued as U.S. Pat. No. 5,859,274 on Jan. 12, 1999.
U.S. patent application Ser. No. 08/307,316 filed 16 Sep. 1994 in the names of Peter S. Kirlin et al., which was issued as U.S. Pat. No. 5,679,815 on Oct. 21, 1997; and
U.S. application Ser. No. 07/918,141 filed Jul. 22, 1992 in the names of Peter S. Kirlin, et al., and issued as U.S. Pat. No. 5,453,494;
In yet another aspect, the present invention relates to a vaporizer delivery system, comprising:
a. a sealable housing comprising an internal chamber;
b. a gas inlet and gas outlet in fluid communication with the internal chamber,
c. at least one rotatable spool positioned within the internal chamber for holding a wire coated with a sublimatable solid source material;
d. a heating means communicatively connected to at least a portion of the housing to provide a heated area within the internal chamber at the sublimation temperature of the solid source material;
e. a drive mechanism for moving the coated wire from the rotatable spool through the heated area.
In still a further aspect, the present invention provides for a vaporizer system comprising:
a. a sealable vessel comprising an internal chamber;
b. a gas inlet and gas outlet in fluid communication with the internal chamber;
c. a conductive wire coated with a sublimatable solid source material for introduction into the internal chamber, wherein the conductive wire has a length extending beyond the longitudinal axis of the sealable vessel;
d. at least one motorized mechanism positioned adjacent to the sealable vessel for moving the conductive wire through the internal chamber;
e. a heating means for raising the temperature in the internal chamber to the sublimation temperature of the sublimatable solid source material; and
f. a pair of electrodes positioned in the internal chamber and contacting the conductive wire for passing an electric heating current therethrough.
In yet another aspect, the present invention provides a method for vaporizing and delivering a solid source material to a downstream semiconductor process chamber, comprising:
a. providing a metallic substrate coated with a sublimatable solid precursor material;
b. introducing the coated substrate into a housing having an internal chamber;
c. heating the internal chamber to the sublimation temperature of the sublimatable solid precursor material to form a precursor gas; and
d. moving the coated substrate through the internal chamber wherein the sublimatable solid material coated on the metallic substrate is sublimated to form a precursor gas and an uncoated metallic substrate; and
e. removing the precursor gas from the internal chamber and transporting same to the downstream semiconductor process chamber.
This embodiment further contemplates the step of passing an electric heating current through the coated wire that has a core wire fabricated of an electrically conductive core and coated with a sublimatable solid precursor material.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.